Throughout the semester we will be making measurements. When you do an experiment, it is important to be able to evaluate how well you can trust your measurements. For example, the known value of g, the acceleration due to gravity, is 9.81 m/s2, ("" means approximately equal to). If you make a measurement that says g = 10.1 m/s2, is that measurement wrong? How do you compare that measurement to the known value of g? Suppose you measure some quantity that is not known? You may make a number of measurements, and get several different results. For example, suppose you measure the mass of an object three times, and get three different values, 5 kg, 4.8 kg, and 5.4 kg. Can you evaluate what the real mass of the object is from those measurements?